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    SubjectRe: [ck] Re: [announce] [patch] Voluntary Kernel Preemption Patch
    Hi, can anyone explain this:

    Using Ingo's first patch when I:
    echo 1 > /proc/sys/kernel/kernel_preempt

    my system hang up after 2 seconds aproximately.

    Using Ingo's modifications + Con's it doesn't lock anymore

    and is the best kernel that I have used to test..

    Thanks!


    On Sun, 11 Jul 2004 16:38:53 +0200, Ingo Molnar <mingo@elte.hu> wrote:
    >
    >
    >
    > * Con Kolivas <kernel@kolivas.org> wrote:
    >
    > > Ok I've done one better than that ;) I had wli help make some
    > > instrumentation for me to help find the remaining non preemptible
    > > kernel portions and set the cutoff to 2ms. Here is what I found:
    > >
    > > 7ms non-preemptible critical section violated 2 ms preempt threshold
    > > starting at reiserfs_sync_fs+0x2d/0xc2 and ending at reiser
    > > fs_lookup+0xe2/0x221
    > >
    > > 9ms non-preemptible critical section violated 2 ms preempt threshold
    > > starting at reiserfs_dirty_inode+0x37/0x10e and ending at r
    > > eiserfs_dirty_inode+0xb0/0x10e
    > >
    > > These seem to be the two offenders. Hope this helps.
    >
    > great!
    >
    > meanwhile i spent an afternoon with another latency testing suite:
    >
    > http://www.alsa-project.org/~iwai/latencytest-0.5.3.tar.gz
    >
    > it was reporting more accurate latencies, except that there were strange
    > spikes of latencies. It turned out that for whatever reason, userspace
    > RDTSC is not always reliable on my box (!).
    >
    > I've attached two fixes against latencytest - one makes rdtsc timestamps
    > more reliable, the other one fixes an SMP bug in the kernel module (it
    > would lock up under SMP otherwise.).
    >
    > here's a latencytest QuickStart: 'cd latencytest; make', then
    > 'insmod kernel/latency-test.ko', then 'cd tests; ../bin/run_tests'.
    >
    > Assuming you have RTC and audio enabled in your kernel it should work
    > fine. It produces PNGs in the same format as Benno's latencytest suite.
    >
    > Ingo
    >
    >
    >


    --
    []s,

    André
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